The lucrative business that could flow from mobile banking is one cash cow that profit-starved US banks don’t need to nickel-and-dime customers in order to milk.

A new study by Aite Group shows that banks that ramp up their mobile services to small business — an untapped market of businesses generating less than $20 million in annual revenues — could reap major rewards.

Forty-five percent of these same businesses with mobile arrangements today already spend more than $50 monthly, $600 annually, on bank products and services. And they tend to have more bank accounts than non-mobile customers.

Paul Merski, chief economist at the Independent Community Bankers Association, says banks that adopt strong mobile platforms for commercial accounts are in a win-win situation.

“The whole banking platform is becoming more electronic and more mobile, particularly for small business owners that don’t have time to make trips to the bank,” Merski told The Post

Still, mobile has some catching up to do.

Many banks don’t offer a full suite of mobile banking, such as online account access, payroll services and online payment approvals and authorization.

About 65 percent of US banks with assets of more than $10 billion offer mobile banking to their small-business customers, compared with 30 percent for banks with less than $10 billion. Only 20 percent of credit unions offer mobile.

The study also recommends that banks bundle mobile banking with other business-banking services.